Cognitive deficits persist despite the availability of effective therapies for HIV. New data indicates that, in contrast to men, delayed memory impairments are a central feature of cognitive impairment in HIV+ women. Furthermore, stress interacts with HIV serostatus to negatively impact verbal memory in particular. This application proposes to investigate stress-associated increases in glucocorticoids (GCs) as a potential contributor to verbal memory deficits in HIV+ women. GCs are released after a stressor and are the key mediator of the relationship between stress and memory dysfunction in non-HIV-infected individuals. Correlational evidence suggests that healthy women are more vulnerable to the cognitive effects of GCs than healthy men. Here we propose to extend this research to HIV and specifically examine the causal role of GCs response on cognitive function. Specifically, we propose to investigate sex differences in the impact of hydrocortisone on cognitive function in HIV in a double-blind, placebo-controlled, cross-over study in 82 HIV+ adults (41 men, 41 women). An innovative feature of this design builds on recent evidence that the effects of GCs on cognition depends on the timing of the cognitive assessment in relation to stress hormone exposure. Therefore, we propose to examine how GCs impact cognitive function both acutely (30 minutes post- intervention) and after a delay (240 minutes post-intervention). We hypothesize that the magnitude of acute and delayed impairments on verbal memory will be greater in HIV+ women compared to HIV+ men. To the best of our knowledge, this will be the first pharmacologic challenge study to elucidate the cognitive effects of GCs in HIV. Such a demonstration will provide critical insights into stress-related increases in GCs as a mechanism underlying the apparent greater deficit in verbal memory in HIV+ women compared to men. Identifying this mechanism is a critical first step in the design of clinical trials aimed at lowerng stress and GCs in order to improve cognitive function, particularly in HIV+ women.